October 1997 Field Journal 10.26 Lesser Black-backed Gull
Technical Details:
Species: Lesser Black-backed Gull Larus fuscus
Date Observed: 10/26/97
Observer: Mark Eaton
Other observers: Dan Singer, Alan Hopkins
Location: Field east of the railroad tracks which, in turn are east of Alviso Marina, in the city of Alviso, county of Santa Clara.
Time Observed: Roughly 6:30 AM through 7:30 AM
Lighting: Before the sun appeared over the east bay hills, good but somewhat dim light. Thereafter, looking nearly directly into the sun. Flare was definitely an issue.
Weather: Cloudless and calm
Optics: Swift Telemaster 10-60x at 30x, supplemented with views of key details through a Kowa TSN-4 and a Celestron C90.
Distance: Roughly 200 yardsBelow are my Field Notes, edited only for grammar and clarity.
Discussions were held with Dan and Alan and field guides were
consulted as well.A [adult] gull noticeably smaller than a Herring Gull. Mantle medium
dark grey, darker than the mantles of the California Gulls in the
vicinity and much darker than the mantles on the Herring Gulls in the
vicinity. Legs bright yellow, though legs on some California Gulls
approached the intensity and saturation of color. Webbing on feet
appears pink with sun shining through them.Head small; the bird appeared to be particularly short-necked.
Forehead very shallow. Pale eye; head white with dark streaks [on
sides of face in the vicinity of the eye]. Streaking on head appears
desner near eye, giving impression of faint eyeline fore and aft.
Bill relatively petite, with upper mandible strongly curved at the
tip. Lower mandible has (very) large oblong red patch, much larger
than found on a Herring Gull. Red spot perhaps as large as 30% of the
length of the lower mandible. Tail appears very worn, giving the
impression of very long wings. [No coloration observed on tail].Primaries very worn; perhaps missing at least one primary (P2?).
[Scapulars] edged in white. Outermost primaries present (P1?) very
worn, with at least 10% bare down to the shaft. Outermost primary
much longer than any other of the primaries present. Significant gap
between outermost primary and next (present) inner primary. Inner
primaries much greyer than outer primaries. No white spots on the
tips of the primaries on the right wing. Spots on inner primaries
larger than on outer primaries. Both outer primaries worn all the way
to the base of what would be the white spot.Vocalization: None noted.
Behavior: The bird flew into the field shortly after first light and
was spotted behind another gull by Dan Singer. The flock was
rearranged by a passing train and, fortunately, the bird settled again
at western edge of the flock, allowing a completely unobstructed
profile view of the bird for some time. After preening and walking
about for most of the hour, the bird went to sleep.Habitat: The field in which the bird was found is on the
south-easteren edge of a large group of ponds just north of the Alviso
Marina. This area is teeming with bird life, though only gulls were
found in the barren field in which the bird was found.Discussion: From mantle color alone, most other common gulls can be
ruled out. Western Gull _Larus Occidentalis_ (of which none were
present during the observation) can be ruled out due to a significant
disparity in size. As well, Slaty-backed Gull _Larus schistisagus_
can be similarly ruled out. Black-tailed Gull _Larus crassirostris_
can be ruled out by bill pattern.Within _Larus fuscus_, the back and saddle color of _L.f. fuscus_ can
be ruled out. Finally, we are left with _L.f. graellsii_. The plate
216c in Harrison, "Seabirds, an identification guide", appears to
perfectly match the bird, albeit with quite a bit less wear to its
plumage. However, after much discussion on this issue from Joe
Morlan, Steve Rottenborn, Nick Lethaby and others, several other
species Palearctic species/subspecies, particularly, _L.a. heuglini_
can not be ruled out.Home
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